firm

The third of these martial virtues, firmness is likewise associated with
the stance of Satan in Paradise Lost. He opens the debate among
the fallen angels in Book II by asserting their democratic unity in
opposition to God, twice calling attention to its presumed stability through
employing the adjective "firm":

With this advantage, then
To union, and firm faith, and firm accord,
More than can be in Heaven, we now return
To claim our just inheritance of old.